Processes for producing aromatic substituted aliphatic acids and their derivatives via palladium catalyzed carbonylation reactions are of great interest. Several palladium catalyzed processes for producing aromatic substituted aliphatic acids from olefins have been described, including those disclosed in GB 1 565 235 (1980), U.S. Pat. No. 5,315,026 (1994), U.S. Pat. No. 5,315,028 (1994), U.S. Pat. No. 5,482,596 (1996), U.S. Pat. No. 5,536,870 (1996), and WO 98/30529 (1998). Another convenient route to aromatic substituted aliphatic acids and their derivatives is a palladium catalyzed carbonylation utilizing aromatic substituted alcohols or aromatic substituted all halides. Such processes have been the subject of previous studies, including those reported in JP Kokoku 56-35659 (1981), JP Kokai 59-95238 (1984), JP Kokai 59-95239 (1984), E.P. 338852A1 (1989), U.S. Pat. No. 4,981,995 (1991), and U.S. Pat. No. 5,322,959 (1994).
Two possible isomers may result from the palladium catalyzed carbonylation reaction, one in which the carboxyl group is bound to the alpha carbon, and one in which the carboxyl group is bound to the beta carbon. When the desired carbonylation product is one isomer, formation of mixtures containing both isomers becomes a problem because they are difficult to separate.